Panel selector contact shoe



Feb. 29, 1944. Q L, VAN lNwAGEN, JR 2,343,100

PANEL SELECTOR CONTACT-SHOE I Filed Oct. 16, 1942 TRAVEL Y Il 1.6 [s

/NVENTOR By c. L. m/NMGE/v Je.

ATTORNEY Patented Feb. 29, 1944 2,343,100 y PANEL SELECTOR CONTACT SHOE Charles L. Van

Inwagen, Jr., Rutherford, N. J.,

assignor to Bell Telephone Laboratories. Incorporated, New York, N. Y., a corporation of New York Application October 16, 1942, Serial No. 462,234

4 Claims.

This invention relates to selector brushes for automatic switches and more particularly to a contact-shoe adapted for use with a brush carriage of the kind shown and described in Patent 2,285,657, issued to C. N. Hickman on June 9, 1942, said brush carriage being part of the so-called high speed panel type of selector switch shown and described in Patent 2,240,039, issued to C. N. Hickman on April 29, 1941. f

A contact-shoe for this type of switch generally comprises a non-conducting support sultably secured to a spring mounted upon the brush carriage, and a central metallic element embedded in the support for engaging the terminals of a bank over which the brush moves during a selection operation, the metallic element of the shoe being conductively connected Vto the spring to provide circuit-completing .facilities between the terminal engaged by the shoe and external control apparatus. Since the spring of a brush is pretensioned for electrical contact with an engaged terminal on the bank, and since the terminals are equally spaced by a distance slightly greater than the length of the metallic element, the shoulders of the non-conducting support are made sufficiently long for each of them to bridge two terminals at the same time to insure nonbridging of two adjacent terminals by said element when the latter becomes momentarily positioned therebetween during a selection operation. The shoulders slope away from the contact element and are adapted to engage the inner edges of the oppositely disposed terminals between which the contact element is positioned so as to provide an inclined surface for the shoe whereby the brush, as it moves over the terminals, is caused to spread out again until the contact element of the shoe becomes centered upon the terminal.

It has been found, however, that, in many instances, the edges of the terminals engaging the shoe dig into the shoulders of the support and cause the latter, during a selection movement of the brush, to snag bank and thereby impair operation of the tor that is, the brush carriage thereof.

It has also been determined that, over long periods of operation, the constant rubbing of the non-conducting support of the shoe with the terminals over which the shoe rides causes the support to be worn down or chipped off and the substance thereof deposited upon the terminal edge, causing thereby the deterioration of the support and the contamination of the terminal, thelatter to the detriment of the circuitito beestabselecagainst the terminals of the '4 lished over the terminal and the contacting element of the shoe.

It is the object of the present invention to provide a contact shoe which, having a .suitable slightly underflush non-conducting support, presents an all-metal surface to each of the terminals to be engaged by the shoeduring a selection operation,k which will preservethe present sliding approach of the shoe to the terminals and yet be non-bridging therebetween. Thus the terminals, prevented from coming into contact with. the non-conducting support, cause the latter to be preserved against the formation of snagging pockets while the terminals themselves are kept free from contamination.

Referring to the drawing:

Fig. 1 shows a perspective view of the contactshoe of my invention with a bank terminal indicated in the contacting position thereof, the spring portion of the shoe which is attached to the brush carriage not being shown.

Fig. 2 is an exploded view of the contact-shoe, the component metallic elements of which have been displaced somewhat with respect to the sup port therefor in order to show more clearly their relationship to the latter and to each other;

Fig. 3 shows a cross section of the contact-shoe taken along the section line 3--3 of Fig. 1; while Fig. 4 shows a front elevation of the contactshoe.

Referring to the gures of the drawing in which identical designations refer to identical parts, the contact-shoe. comprises a metallic element I formed at the end of the brush spring 4 which is attached to the brush carrier in the manner y shown in the above-mentioned patent to Hickman, the guide pieces 2 which are supported on the top of element I as explained below, and a support 3 into which are embedded the element I and the tongues 9 and I2 of the guides 2, said support 3 being made of any suitable insulating compound such as, for example, shellac, mica, hard rubber, glass, etc.

The contact element I is, as before stated, formed at the end of brush spring Il, the remaining portion of the latter (not shown) being, in form and construction, identical with the tip andi ring brush springs of the panel selector brush shown in the above-mentioned patent to which reference is made for a description of the spring, the component parts of the entire brush assembly and the mode of its operation.

The contact element I is punched out of a desired spring stock in the form indicated in Fig. 2, said element having two spaced but aligned arcuate bands I9 and II between the outer' rectangular portion I3 and the body portion of spring 4, In between the bands I0 and II, are oppositely disposed downwardly bent tongues 5 which are provided to insure lateral rigidity for the element l when the same is embedded in the support 3 as explainedbelow, Circular apertures 'I' and 8, the formerpunched in the center of the outer rectangular portion of spring 4 and the latter punched to the left of the bands in the body ofsaid spring coaxially with aperture 'l and equidistant from the nearest tongue- 5, have diameters slightly larger than the width of tongue I2 of guide piece 2 and serve as non-contacting slots for the passage therethroughk of said outer tongues I2 when the two guide pieces 2 are superimposedly tted upon the element I on either side of the bands I0 and Il. These apertures 'I and El, however, need not be circular as, indeed,

they may be, if desired, of rectangular conguration. The space between the two bands I--and lI shall be suniciently wide notionly to permit the free passage therethrough o f tongue 9'of the guide piece 2- but, when the guide piece is fitted over the element I, shall also be wide enoughto keep the edges of the tongue out of contactwith the inner edges of the bands I Il and4 II.

The guide pieces 2, which are symmetrical and formed into the shape indicated in Fig. 2, may be produced, if desired,l from` the same spring stock as Contact element I. These guide pieces, however, need not have the same electrical properties as element I since they function merely as insulated metal guides for the brush spring 4 asv outer tongue I2V of` the. guide piece ispassed through the holel of the contact element I, v the convex surface of tongue 9 will be lush with the near edges of the bands, to provide continuous metallic contact to a terminal moving over the surface of either' guide piece 2 into engagement with the crests of thebands. The perpendiculai' portionsof Atongues 9 and I2 aredimen-- sioned to insurethat when the lower edges of, both tongues rest on the same horizontal plane` at the bottom of the, support 3, the part of the convex surface of tongue 9 which isin alignment with the, nea-r edges of thebands shall be flush with said edges and the rest of the guide .piece shall assume an inclined positionaway, from the bands that will provideaterminal to be engaged with a gradual up-hill surface from the edgeB of the support, when the shoe is between terminals, to `the crest of the` bands when ,the latter, engage the terminals for proper Contact closure.

In producing the contact-shoe the contact ele-v ment I formed at the end of spring 4 is, inserted. intoa xture (not shown) with each ofthe guideL pieces 2 fitted to the .top thereof on either side of the bands IilandII by inserting tongue I2in hole 1 (or 8), vand tongue 9 .inT the space inter-` Thedepth of. the, fxtmeo rnediate the,bar1 dS-. the base of'which the bottom edges of tongues ill.

9 and I2 of each guide piece come to rest is such that that portion of the convex surface of tongue 9 looking toward tongue I2 comes flush with the lower edges of bands I0 and II, and since the length of the bent portion of tongue I2A is less than that of tongue 9 by an amount that will give each guide piece the required angularity with respect to the crest of the bands IIl and II, each of said guide pieces assumes a sloping position outwardly from theplace where the convex portion of tongue 9 is nearest to the edges of bandsY I0 and II. This leaves a wedge-shaped space between the under surface of each guide piece and the upper surface of contact element I lying on either side of the bands which is filled with insulating compound.

The fixture includes a suitable mold of support 3ir1to which is poured, in melted form, the non-conducting compound of which said support is made, said compound filling all the interstices between the guides and the element. Incooling and solidifying, the compound adheres to the under surfaces of guide pieces 2'and both surfaces of the bands ID and II except the upper exposed parts thereof, the tongues 9 and I2 forming a rigid structure with the exposed surfaces 0f bands IU and Iliianked by the upper surfaces of the guide pieces 2 to form shoulders sloping away from said central element. The exposed insulated support 3 is slightly underflush with the top metallic exposed parts of the shoe which are then buied and polished. The insulated support, when solidified, assumes the shape and structure 3 indicated in Fig. 2.

When the appropriate number of contact-shoes are assembled as a brush structure of the. type shown in the above-mentioned Patent 2,285,657 to Hickman, and said brush is mounted on the brush carrier with the latter positionedwith respect to a row of terminals as indicated in said patent, a. contact-shoe, if Yproperly vadjusted with respect to the terminals of the bank it will lengage, will have the crests'of bands rII) and II in substantial alignment with the-edge ofthe terminal,-say terminal I4. When the brush carrierismovedfor thefselection of a terminal inthe bank, the springs 4 of-thebrushselected for operation are tensioned against the terminals so hat, between terminals, the exposed surfaces'of ands tionedposition so that,at any timethe exposed band surfaces will `engage the one terminal. only. When-the brushV moves to theright or. left-de.- pending upon the direction of trayelassumethat the, brush is travelingztowards theright as indicated-in Fig. -1),l the terminal ongthe rightgof the brush wi ll,rinefl`ect, follow Vthe surface of the right guidepiece 2 until the center portion of the terminal reaches the lower edges of the'bands .In and l. The terminaiwiii then beiifted (cammed up) on to the crests vof the bands I0 and-II without snagging.

What is claimedis: Y

1. A multiple brushk contact-shoe fora panel bankselector comprising a formed insulating supe, port, y a Vmetallic contacting element embedded therein, and a metallicguide onleither sidethereof to provide va continuous metallic surfaceto an externaljbody moving Athereacross to engagesaid, metallic element..

2. A multiple brush contact-shoe for a panel IIlland I I of the shoe will haveatendency tOJIOdgefbetWeenthem, but Kthe lengthV of theishoebetween .the two extremes of thesupport 3,1 is not suicient'to cause ittofengagethehigher' and lower terminal whenthe shoe is in the men-A bankl selector comprising two metallic guides, a contact element disposed thereunder with an exposed. surface Vtherebetween, and a formed insulating support for said guides and said contact element, whereby a bank terminal of the selector will continuously engage a metallic surface as said contact-shoe is caused to move transversely with respect to said terminal.

3. A multiple brush contact-shoe for a panel bank selector comprising a formed insulating support, two metallic converging elements embedded in said support to provide an inclined runway to the center of said support, and two raised contact portions one embedded on each side on the longitudinal axis of said support to provide an arcuate approach to the center of said contact portion from the inner end of each of said two metallic elements.

4. A multiple brush contact-shoe for a panel bank selector comprising a contact element having two spaced arcuate bands terminating in supporting portions, each of said portions having an aperture therein, a metallic guide fitted over each of said portions having a rst member passable through the space intermediate said bands and a secondmember passable through one of said apertures, the lengths of said first and second members being determined by the degree of inclination between the upper surfaces of said bands and said guide, and a non-conducting support molded beneath said element andadhering to the supported guides through contact with said rst and second members thereof, said elements and said guides being so disposed relative to one another upon said support as to be insulated from each other and to present a continuous metal surface to a body moving over the surface of either guide to engage said contact element.

CHARLES L. VAN INWAGEN, JR. 

